Filled calender roll



Feb. 6, 1968 W. H. HOGE 3,367,008

FILLED CALENDER ROLL Filed April 13, 1966 I6 FIG.1 1

FIG. 3

FIG. 4

INVENTOR. WILLIAM H. HOGE ATTORN EYS United States Patent Ofiice3,367,008 Patented Feb. 6, 1968 3,367,008 FILLED CALENDER ROLL WilliamH. Hoge, Flemington, N.J., assignor to Riegel Paper Corporation, NewYork, N.Y., a corporation of Delaware Filed Apr. 13, 1966, Scr. No.542,381 8 Claims. (Cl. 29-125) The present invention relates to calenderroll filling paper and to calender rolls incorporating such paper and,more particularly, to a new and improved filled calender roll andfilling paper therefor, which is characterized by significantly improvedresistance to degradation by heat.

In the finishing of paper it is often desirable to direct a web througha supercalender stack of alternate metal and fiber-filled calenderrolls, the nips of which subject the traveling web to sufficientpressure and rolling friction to smooth, to polish, and to provide manyother desirable properties and characteristics thereto. The alternate,fiberfilled calender rolls typically are comprised of metal cores havingaxially spaced end plates and having the spaces between the platesfilled with a large plurality of disks comprised of cotton, paper, orlike fibrous materials, maintained under axial compression.

In the calendering operation, substantial heat is developed in the rollfilling, the extent of which is dependent upon such factors as the speedand pressure of calendering as well as resilience of the filled rolls.Moreover, in certain calendering applications, the metal rollsthemselves are also heated by supplying steam thereto, thereby furtherelevating the temperature in the filled rolls. Operation at hightemperatures has a deleterious effect on the filled rolls, whichaccelerates their degradation through the development of local hot spotswithin the roll and through cracking or other mechanical failure of thefiller I disks.

To the end of decelerating the thermal degradation of filled calenderrolls and prolonging their effective lives, it has been proposed tofabricate the filled rolls from fiber disks composed of heat resistantmaterial such as asbestos paper, asbestos cloth, or equivalent heatresistant sheet materials, such as paper or cloth impregnated with aheat resistant composition. Alternatively or additionally to the use ofheat resistant filler material, positive cooling of the core of a filledcalender roll With a circulating liquid coolant such as water has beenproposed to retard the thermal degradation of the filler disks. However,these prior proposals have not resulted in a commercially practicablesolution to the problem of thermal degradation.

It is the primary object of the present invention to provide a calenderroll, more specifically, a calender roll filler material, which willhave a superior life and an enhanced resistance to thermal degradationin comparison to known and available calender rolls and calender rollfillings. In accordance with the principles of the invention, it hasbeen determined that the aforesaid object may be realized, i.e., that acalender filling paper or material may have its useful life in acalender roll greatly extended, by having one or both sides of thecalender filler disks metallized with a film of metal of molecularthickness, the metallizing material advantageously being of the typewhich may be applied in a vacuum by vapor deposition techniques. Withoutnecessarily altering the composition of conventionally availablecalender paper, the radial direction thermal conductivity of a filledcalender roll may be greatly improved and its effective operating lifethereby significantly extended.

In conjunction with the improved calender roll filling, it may beadvantageous to utilize a water-cooled core shaft. By reason of thesignificantly improved radial heat conductivity of the new filling,heretofore unrealized advantages may be derived from the forcedconvection removal of heat conducted radially inward to the roll core.

For a more complete understanding of the present invention and itsattendant advantages, reference should be made of the folowing detaileddescription taken in conjunction with the accompanying drawing, inwhich:

FIG. 1 is an elevational view of a new and improved calender roll filledwith metallized calender paper in accordance with the inventiveprinciples;

FIG. 2 is a cross-sectional view of the calender of FIG. 1 taken alongline 22 thereof;

FIG. 3 is an enlarged fragmentary view showing adjacent metallizedcalender disks; and

FIG. 4 is a greatly enlarged, fragmentary, cross-sectional view of thenew and improved calender filling material.

With reference to FIG. 1, the calender roll 10 of the present inventionmay be conventional in most respects with the exception of the actualfiller material 9. Thus, the roll assembly includes a supporting coreshaft 11, the opposite ends of which are threaded to receive threadedcompression caps 13 which maintain a large plurality of calender disks15 under very high compression. The core shaft 11 advantageouslyincludes a cooling tube 12 disposed concentrically therewith and throughwhich water or some other coolant may be circulated to reduce thetemperature of the calender roll assembly 10 during its operation. Aswill be understood, a filled calender roll may be assembled by stackinga plurality of the calender disks 15 on the core and then subjectingthem to substantial compression by the members 13 to form an effectivelysolid, hard roll body. A uniform, cylindrical Working surface 16 isthereafter established on the calender by turning down the edges of thecompressed disks 15 in a lathe.

The actual dimensions of the calender roll are determined by the type ofsupercalender stack in which it is to be employed, the type of finishwhich is to be applied to the paper being processed in the stack, andthe dimensions of the paper being finished in the stack. Accordingly,the outer diameter of the working surface 16 may range fromapproximately 10 to 20 inches and may have an effective length rangingbetween 60 and 200 inches, for example. The bore dimension of the innerdisks corresponds to the outer diameter dimension of the core element11, which will be determined by the size of the finished calender rolland the use to which it is to be put. By way of more specific example, afilled calender roll having a length on the order of 72 inches and anouter diameter on the order of 13 /2 inches may have a bore of about 7inches in diameter.

In accordance with the principles of the present invention, the new andimproved filler disks 15 are made from papers 20 which are especiallyreceptive to a vacuum deposited metallized coating or super thin film 21and r are especially stable during the application of the film.

A preferred sheet is manufactured from a cotton rag furnish and has abasis weight of approximately 40 pounds per ream, a moisture content ofapproximately 3%, and a light size press-applied coating of a fullyhydrolyzed high viscosity polyvinyl alcohol. The treated paper has themetallic film applied thereto when it is transported as a web through ametallizing chamber maintained under a vacuum of approximately 0.5 to2.0 microns of mercury, in which aluminum or some other metal is heatedto its vaporization point. The metallic vapor is condensed upon one orboth sides of the moving paper to form an extremely thin,vapor-deposited metallic film 21 thereupon, the thickness of which maybe on the order of 3 millionths of an inch. Although the film thicknessis not measurable by ordinary measuring techniques, one accepted basisfor measuring the thickness of deposited metal films of this type is bymeasuring electrical resist- "9 time in the plane of the sheet, whichfor the film 21 may be within the range of approximately 3 to 20 ohmsper square. For a more detailed description of the method and techniquesof depositing thin films and ascertaining their thicknesses,referencemay be had to such works 8 Vacuum Deposition of Thin Films by L.Holland, John Wiley & Sons, Inc., 1960.

While the new filler paper 20 is especially well suited for the purposesof the present invention, being receptive to a vapor deposited coatingand being stable during the vacuum deposition process, it should beunderstood that manyof the known conventional calender papers may beprovided with avacuum deposited metal film to enhance its properties inaccordance with the teachings of the presentinvention. When the newmetallized paper disks are initially assembled on the core shaft 11 ofthe calender roll, they are approximately only 40% of their ultimatedensity. However, they are subjected to sufiicient pressure between thecompression elements 13 to increase their density to the ultimate value,approximately 500 disks (of paper of 40 pounds per ream initial basisweight) per inch of calender roll face. As will be understood, ofcourse, the nature of the treatment and the specific caliper and basisweight of the base sheet will cause variation in the number of calenderdisks per inch.

It will be appreciated that a calender roll made from metallized paperin accordance with the teachings of the present invention will be freeof localized hot spots, Will have better thermal conductivity, andtherefore will greatly outperform and outlast conventional calenderrolls. Particularly advantageous results may be realized through theutilization of the new, metallized filler paper in ,combination with awater-cooled core shaft. The new filter material enables generated heatto be conducted efficiently in a radially inward direction, from thhecalender nip to the core shaft of the roll, from which it may be removedby the circulating cooling fluid.

' Although the concepts of the invention are applicable to a widevariety of filler papers, optimum benefits are realized using papers ofrelatively low basis weight, which result in a high relative proportionof radial heat-conducting paths. Also, where desired, the paper may bemetallized on both sides.

It should be understood that the specific embodiment of the inventionherein illustrated and described is intended to be representative only,as certain changes may be made therein without departing from the clearteachings of the disclosure. Accordingly, reference should be made tothe following appended claims in determining the full scope of theinvention.

What is claimed is:

1. In a calender roll of the type comprising a supporting core elementand a plurality of paper disks supported thereupon under compression bya pair of axial elements, the improvement wherein a film of metalcondensed from its vapor state is applied to said paper disks on atleast one of the sides thereof.

2. A calender roll in accordance with claim 1, in which said metal isaluminum.

3. A calender roll in accordance with claim 1, in which said coating isapproximately 3 millionths of an inch in thickness.

4. A calender roll in accordance with claim 1, in which said paper has abasis weight of approximately 40 pounds per ream.

5. A calender roll in accordance with claim 1, in which said coating hasa specific resistivity of from about 3 to 20 ohms per square.

6. A calender roll in accordance with claim 1, in which said paper disksare coated with fully hydrolyzed high viscosity polyvinyl alcohol.

7. In a calender roll of the type comprising a supporting core elementand a plurality of cellulosic disks supported thereupon undercompression by a pair of axial elements, the improvement wherein asubstantially continuous heat conducting, vaporized metal film isapplied to said cellulosic disks on at least one of the sides thereof,said vaporized metal film extending between the face of said roll andsaid core element and providing a heat conducting path therebetween.

8. A calender roll in accordance with claim 7, in which said coreelement includes an internal passage through which a cooling medium mayflow freely.

References Cited UNITED STATES PATENTS 34,394 2/1862 Critcherson 29125 X1,628,835 5/1927 Furbush 29125 1,739,572 12/1929 Bidwell 93 2,987,8026/1961 Quinn 29-132 X 3,036,549 5/1962 Iwata et a1 117107.1 X 3,040,7026/1962 Eng et al 117-l07.1 X 3,291,039 12/1966 Christie 29-125 X.

LOUIS O. MAASSEL, Primary Examiner.

1. IN A CALENDER ROLL OF THE TYPE COMPRISING A SUPPORTING CORE ELEMENTAND A PLURALITY OF PAPER DISKS SUPPORTED THEREUPON UNDER COMPRESSION BYA PAIR OF AXIAL ELEMENTS, THE IMPROVEMENT WHEREIN A FILM OF METALCONDENSED FROM ITS VAPOR STATE IS APPLIED TO SAID PAPER DISKS ON ATLEAST ONE OF THE SIDES THEREOF.